The Grass Doctor

Why Does My Lawn Have a Rust Color Dust Coming From the Grass ?

This fall my lawn has had a rust colored dust that collects on shoes and lawn mower. The grass does not appear rust color, maybe a little stressed. I put a nitrogen fertilizer (Loveland Renovator) on my lawn. I guy at the lawn & nursery store said my lawn probably has a fungus on it. But I'm wondering if I've over fertilized my lawn. Can over fertilizing a lawn make it discolor or rusty?

Public Comments

1. The powder is actually millions of microscopic spores produced by a fungus called rust. There are several different rust fungi that cause rust. The most common one on Kentucky bluegrass, annual bluegrass, fescues and ryegrasses is Puccinia graminis. A separate species, Puccinia zoysia can infect zoysia grass. Rust becomes a problem when grass plants are growing slowly. When grass plants are growing fairly rapidly, leaf tissues are removed by mowing at relatively frequent intervals, and the disease does not become apparent. With grass plants that are growing slowly, the fungus has sufficient time (7-14 days) to produce the microscopic spores in infected leaf tissue. These spores are then wind-blown or splashed by rain or irrigation to other leaves, where new infections can occur. Consequently, the disease can become very severe when certain weather conditions occur when the grass is growing slowly. Leaf infections occur most frequently when days are dry and windy followed by heavy dew formation at night. The dry, powdery spores are easily disseminated by wind currents. Rust, by itself, rarely kills a grass plant, unless other stress factors are involved. Rust infected plants are weakened. When the disease continues into late fall, infected plants may become more susceptible to winter injury. Young seedlings are highly susceptible, and proper water and fertility management may be required for early fall seedings. The rust fungi rarely survive the winter in Indiana. The disease organisms survive winters in infected tissues in the southern and southwestern states. Spores of the fungi are wind-borne in spring and summer from those areas and the disease moves northward into Indiana and surrounding states, usually in July and August. Control of rust in the home lawn is best accomplished by fertilizing and irrigating, as needed, to promote grass growth. Do not promote excessive growth. Water infrequently, but deeply. Irrigate during the early part of the day. Irrigate at a time that will permit complete leaf dryness before dew formation. Watering in the evening will increase the length of time that free moisture is on the leaves and will increase the chances of infection. Mow frequently and collect clippings when possible. Several fungicides will aid in the control of rust, but multiple applications are generally required, and you might choose to achieve control via management practices first. You may find products containing chlorothalonil or mancozeb being sold under various trade names at garden supply stores or nurseries.
2. http://en.allexperts.com/q/Lawns-725/Rust-colored-lawn.htm From the above-posted link Rust" is the name for the orange or yellow-orange spores which is found on grass especially in late summer to early fall when weather is dry. The spherical shapes are called pustules and they come off easily when rubbed. It is therefore easy to get on your shoes, etc. Typically lawns which is not growing actively due to low levels of fertility (fertilizer) are susceptible to rust. However, it does not have to be due to lack of fertilization. Cool season grass are often affected by very hot or dry summers which can also result in less active growth and make them suceptible to rust. Finally, heavily watered lawns (or lots of rain) can wash out nitrogen from the soil (especially on sandy loam bases) which can have same effect. There is not much you can do now, and you definitely do not need any fungicides, etc. However you can change some horiticultural factors as follows: - fertilize in september and october using a high nitrogen fertilizer (such as Scott's Turfbuilder 29-3-4). - water infrequently and deeply if you do water. Try to water maximum twice per week and when you water, water deeply (45-60 minutes each time). Try to water in early morning hours, or alternatively at night after dew fall. Avoid fertilizing in late afternoon or early evening. If you have not done so already, I also recommend that you have a soil test done. If phosphorous or potassium levels show below optimum, it may be a good idea to use fertilizers with higher levels of these. For example, the so-called "Starter fertilizers" have higher levels of phosphorous and the so-called "Winterizers" have higher levels of potassium. If needed, substitute these for your usual (normal) type fertilizer as needed.
3. Dear Rusty, It is more than likely that the guy at the nursery is correct. Treatment for such problems are readily available. You have thought about the breathing problems this has the potential to present to your family.